1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device.
2. Description of Related Art
Active matrix LCD devices, where thin film transistors (TFTs) and pixel electrodes are arranged in the form of a matrix, have been widely used due to a high resolution and an excellent performance of implementing moving images.
FIG. 1 is a cross-sectional view illustrating a liquid crystal panel of a typical active matrix LCD device. As shown in FIG. 1, the liquid crystal panel 20 includes lower and upper substrates 2 and 4 with a liquid crystal layer 10 interposed therebetween. The lower substrate 2 is divided into two regions: a region S; and a region P. TFTs are arranged on the region S as a switching element, and pixel electrodes 14 are arranged on the pixel region P. The upper substrate 4 includes a color filter 8 and a common electrode 12. Through the pixel electrode 14 and the common electrode 12, voltages are applied to the liquid crystal layer 10. In order to prevent a leakage of the liquid crystal, edge portions of the two substrate 2 and 4 are sealed by a sealant 6.
The TFTs receive electrical signals from an external drive IC (integrated circuit) to drive the pixel electrodes 14. Each of the TFTs includes a gate electrode, a source electrode and a drain electrode. The gate electrode extends from a gate line, and the source electrode extends from the data line. The gate and data lines have gate and data pads on their end portion, respectively. The gate and data pads are electrically connected with the external drive IC.
The drive IC is divided into a gate drive IC and a data drive IC. The gate drive IC is electrically connected with the gate pad to control the gate electrode, and the data drive IC is electrically connected with the data pad to control the source electrode.
A technique for connecting the drive IC with the liquid crystal panel 20 includes a COB (chip on board), a TAB (tape automated bonding), and a COG (chip on glass).
Of these, the TAB technique is in most wide use for LCD devices having a high resolution, for example, a resolution of 600×800×3 or 1024×1280×3. The TAB technique is one that the drive IC is mounted on a tape carrier. What the drive IC is mounted on the tape carrier is called a tape carrier package (hereinafter referred to as simply “TCP”).
FIG. 2 is a perspective view illustrating a structure of connecting the liquid crystal panel with a TCP using the TAB technique. As shown in FIG. 2, a drive IC 51 is mounted on the TCP 50. The liquid crystal panel 20 is electrically connected with a PCB (printed circuit board) 52 through the TCP 50.
A process for manufacturing the TCP includes an inner lead bonding process, an encapsulating process, and an outer lead bonding process. Through the inner lead bonding process, the tape carrier that is conveyed by a reel-to-reel method is aligned with a chip on a substrate and the two is connected with each other by a heat energy and a pressure. The chip is coated with an epoxy-based resin to protect the chip and the inner leads through the encapsulation process. Outer leads are connected with pads on the PCB through the outer lead bonding process.
FIG. 3 is a plan view illustrating the liquid crystal panel having a dual bank structure according to the conventional art. As shown in FIG. 3, the liquid crystal panel 20 includes an active region 102 on which images are substantially displayed. Gate drive ICs 100G are arranged on the left hand side of the active region 102, data drive ICs 100D are arranged on top and bottom portions of the active region 102. According to a recent tendency toward a high resolution, the dual bank structure in which the data drive ICs are arranged on the top and bottom portions of the liquid crystal panel is in wide use for the LCD devices. In other words, in case of the LCD devices of an SXGA type having a resolution of 1024×1280×3, since the number of the data lines arranged in a longitudinal direction is three times as many as the gate lines arranged in a transverse direction, it is preferable that the dual bank structure is employed.
However, such a dual bank structure has a problem in that spot effect may occur at a position of the active region 102 near the data drive IC 100D.
In further detail, it is assumed that a first drive IC 100D1 drives odd data lines, and a second drive IC 100D2 drives even data lines. As shown in FIGS. 4A and 4B, data signals from the second data drive IC 100D2 has a more distorted wave form at the position A than that from the fist data drive ICs 100D1 does. This is because RC delays of the two lines are different from each other. As a result, a charging time of a pixel charged at the position “A” by data signals, respectively, outputted from the first and second data drive ICs 100D1 and 100D2 becomes different from each other due to an RC delay, leading to a brightness difference between the odd and even data lines. The brightness difference results in spot effect such as a formation of fine vertical lines at the position A.
For the foregoing reasons, there is a need for a LCD device that overcomes spot effect such as a formation of vertical lines and has excellent display characteristics.